Method of producing vulcanized plastic articles.



- No Drawing.

ran snares rad ans? orrrcn RAYMOND LB. PRICE, OF YORK, N. Y., ASSIGNORT0 RUBBER REGENERATING COMPANY, A CORPORATION OF INDIANA.

METHOD OF PRODUCING VUILCANIZED PLASTIC ARTICLES.

To all whom it may concern Be it known that I, RAYMOND B. PRICE, acitizen of the-United States, residing at New York, county and State ofNew York, have invented certain new and useful Improvements in Methodsof Producing Vulcanized Plastic Articles, of which the following is afull, clear, and exact description.

This invention relates to the method of producing vulcanized plasticarticles, and more particularly to the manner-of drying the plastic onthe form after each submersion in the plastic solution.

In the manufacture of dipped vulcanized plastic articles, the practiceheretofore has been to accumulate the vulcanizable plastic upon a formby repeatedly dipping the form in a solution of the plastic, andsubjecting the form and the plastic thereon after each dipping toatmospheric air for a sufficient interval of time to remove the slventfrom the plastic solution by evaporation. This old and Well knownpractice has certain disadvantages both as to the time consumed in,drying, and as to defects in and lack of uniformity in the thickness orgage of different portions of the same article, or. diiferent articleswhich have undergone exactly the same treatment. in part from thepresence of moisture and dust particles in atmospheric air and thevariances in the quantity of both moisture and dust from time to time.

The evaporation of the solvent contained in the plastic upon a form hasthe effect of chilling the form with a resultant condensation ofmoisture contained in the air upon the plastic. The presence of thismoisture reduces the area of the article fromwhich the volatilization ofthe solvent may be eflected, with a resultant prolongation of the timerequired to properly condition the plastic for another dip or forsubjection to a vulcanizing medium. Furthermore, if I .this condensateis not entirely removed before the form is againdipped in the solution,there is likelihood of blisters being formed. When the article isvulcanized by the'cold cure process, the presence of moisture in thebody of the articlemay result in the formation of hydrochloric acid inthe article thus causing rapid deterioration and poor aging properties.

With the old and well known method above referred to the recovery of the.sol-

Specification of Letters Patent.

These conditions arise Patented Nov. 30, 1915.

Application filed January 16, 1915. Serial No. 2,733.

' from the plastic deposited upon the form at each dipping underconditions which preclude allpossibility of moisture being de posited onthesurface of the article during drying with a resultant elimination ofpossibility ofthose defects in the completed article arisingfromcondensation of the mois ture of the air upon the article.

The drying of the article within an inclosed space and in the presenceof a subatmospheric pressure or vacuum, also has the advantage that thesolvent removed by evaporation or volatilization from the plastic may bereadily recovered and danger of gas intoxication is avoided without theexpense of, or Waste incidental to the apparatus" heretofore used toprotect the workmen. Furthermore, the dangers of the formation of anexplosive mixture of the volatile solvent and air is reduced to aminimum.

The invention consists primarily in the method of producing vulcanizedplastic articles including therein the steps of dipping a form in asolution of vulcanizable plastic and thereafter removing the solvent byexposing the form and the plastic thereon in an inclosed space to asub-atmospheric pressure; and in such other novel steps and practice asare hereinafter set forth and described and more particularly pointedout in the claims hereto appended.

In the-practice of my invention, I submerge a form. of the desiredcontour in a solution of a vulcanizable plastic. The composition of thisplastic may either be such as space, and a vacuum or partial vacuum iscreated and maintained within said space for a sufficient interval toinsure the com-- plete evaporation or volatilization of the solvent inthe plastic. To prepare the article for vulcanization, the form isrepeatedly and alternately dipped and subjected to sub-atmosphericpressure or a vacuum as described.

If desired, the plastic on the form may be subjected to heat which mayif desired be supplied directly to the form itself, which beingsubjected to sub-atmospheric pressure or a vacuum accelerates theevaporation of the solvent. lVhen heat is used it may be applied at anytime during any drying step and in various ways.

By maintaining a sub-atmospheric or reduced pressure about the formwhile the plastic thereon is drying, I not only reduce the time requiredto dry the plastic after each dip, but avoid the presence about the formof atmospheric air containing sufficient moisture to cause thedeposition of moisture upon the plastic as a result of the evaporationof the solvent. As a conse- ,quence those defects in the completedarticle resulting from such moisture are avoided and no time andattention is required to remove any such moisture prior to again dippingthe form. My improved method also admits of the drying of large numbersof articles under substantially identical conditions, irrespective ofchangeable atmosphericconditions.

As the solvent volatilizes, it is withdrawn from the drying chamberunmixed with any substantial quantity of air, and hence a largepercentage thereof may be quickly and cheaply recovered. The withdrawalof the solvent, also prevents waste of the solvent and gas intoxicationof the workmen through the. escape of thesolvent into the dryingroom.

Thelow pressure maintained about the form while within an inclosedspace,- and the short time required to effect a satisfactory drying ofthe plastic, avoids possibility of dust settling upon the plastic whiledryin Y 4 articles made by my improved method seem to have uniformthickness, to be compact throughout and tougher, which I attribute toconditions of surface tension resulting from the action of the reducedpressure.

vent by exposing the form and the plastic thereon in an inclosed spaceto a sub-atmospheric pressure.

2. The method of producing vulcanized plastic articles including thereinthe steps of repeatedly and alternately dipping a form in a solution ofvulcaniz'able plastic and exposing the form and the plastic thereon inan inclosed space to a sub-atmospheric pressure whereby the solvent isremoved after each dip, the deposit of moisture and dust particles uponthe plastic are prevented, and the escape of the volatile solvent isprevented.

Signed at New York, N. Y., January 14, 1915.

RAYMOND B. PRICE.

Witnesses:

.DANIEL A. WILCOX, VERQNICA BRAUN.

